The HTML Help Registration tool is designed specifically for finding, registering, unregistering and replacing compiled Microsoft HTML Help files (.CHM files) in your registry. The process of registering a .CHM file takes place on your local hard drive and is not related to how users view your application Help.
The registry is a database on your local hard drive that stores information about your system in binary form. The registry enables your operating system to "talk" to your program files. When you install a new application in Windows 95/98/NT, it can enter all kinds of information in the registry, such as programs to use when you select file extensions (.exe, .doc., .wri, .pdf, etc.), installation dates, whether a program is a "trial-version" or fully-registered (paid for), what files were installed, and automatic uninstallation information.
The registry also stores information about the system itself, like what hard drives exist, how much RAM is installed, and if IDE drives or 32-bit I/O are enabled.
Because the registry contains so much important information about your computer and files, making changes to the registry is not recommended. In fact, editing the registry improperly can cause serious damage to your operating system and loss of files.
There are cases, though, where you may need to register your .CHM file. If you are creating an HTML Help project for an application, your developer makes the decision about how the application will "call" the Help. Some methods of calling Help require that the .CHM be registered, others do not. Check with your developer and let him or her know that the HTML Help Registration tool is available. Using it enables you to easily register your .CHM file without harming your registry.
Note: You only need to register .CHM files with application Help (not with standalone products).